Collaborative models for autonomous systems controller synthesis

Funding: UK EPSRC grants EP/N508792/1, EP/N007565 and EC/P51133X/1.We show how detailed simulation models and abstract Markov models can be developed collaboratively to generate and implement effective controllers for autonomous agent search and retrieve missions. We introduce a concrete simulation model of an Unmanned Aerial Vehicle (UAV). We then show how the probabilistic model checker PRISM is used for optimal strategy synthesis for a sequence of scenarios relevant to UAVs and potentially other autonomous agent systems. For each scenario we demonstrate how it can be modelled using PRISM, give model checking statistics and present the synthesised optimal strategies. We then show how our strategies can be returned to the controller for the simulation model and provide experimental results to demonstrate the effectiveness of one such strategy. Finally we explain how our models can be adapted, using symmetry, for use on larger search areas, and demonstrate the feasibility of this approach.Publisher PDFPeer reviewe

Gameplay analysis of multiplayer games with verified action-costs

Measuring player skill cannot be done by considering their historical success alone as the relative skill of their opponents must be considered along with confounding factors such as luck and circumstance. With a specifically designed game, every possible player action can be attributed a cost, the value by which a player reduces their maximum probability of winning. By considering the costs of the actions made by a player we can obtain a more accurate representation of how skilful they are. We developed such a game, the mobile game RPGLite, and compared the actions players made with the cost values we had calculated. Through this analysis we made several observations about RPGLite which we share here to demonstrate the utility of action-costs for gameplay analysis. We show how they can be used to identify game states which players have difficulty making the best moves from, to measure how players learn over time and to compare the strengths and complexity of the characters of RPGLite. Commercial titles could benefit from similar tools—we discuss the feasibility of applying our approach to more complex games

An Overview of Verification and Validation Challenges for Inspection Robots

The advent of sophisticated robotics and AI technology makes sending humans into hazardous and distant environments to carry out inspections increasingly avoidable. Being able to send a robot, rather than a human, into a nuclear facility or deep space is very appealing. However, building these robotic systems is just the start and we still need to carry out a range of verification and validation tasks to ensure that the systems to be deployed are as safe and reliable as possible. Based on our experience across three research and innovation hubs within the UK’s “Robots for a Safer World” programme, we present an overview of the relevant techniques and challenges in this area. As the hubs are active across nuclear, offshore, and space environments, this gives a breadth of issues common to many inspection robot

Replication and Abstraction: Symmetry in Automated Formal Verification.

This article surveys fundamental and applied aspects of symmetry in system models, and of symmetry reduction methods used to counter state explosion in model checking, an automated formal verification technique. While covering the research field broadly, we particularly emphasize recent progress in applying the technique to realistic systems, including tools that promise to elevate the scope of symmetry reduction to large-scale program verification. The article targets researchers and engineers interested in formal verification of concurrent systems

Language-level symmetry reduction for probabilistic model checking

Symmetry reduction is a technique for combating state-space explosion in model checking. The generic representatives approach to symmetry reduction uses a language-level translation of symmetric models to a reduced form, making it straightforward to combine with existing tools and implementations. These techniques have been proposed for both non-probabilistic and probabilistic model checking, but are currently difficult to apply to complex models due to prohibitive restrictions in the modelling language. We present a much richer language, which allows specification of probabilistic systems in a way that guarantees the applicability of the generic representatives technique, together with an extended translation algorithm, and demonstrate the effectiveness of our techniques on a large set of case studies

Formal analysis of communication protocols for wireless sensor systems

Sensor technology is an increasingly popular area of research due to the prevalent use of sensor devices. With the need for accurate, detailed data sensors are increasingly often used together in sensor networks. As the size of these sensor networks grows, so does the importance of efficient methods for their analysis for the prevention of system errors and discovery of design flaws. The increasing number of sensor devices leads to an exponential increase is the state space of the associated model. As such models of realistic systems are decreasingly often small enough for their verification to be feasible. Symmetry reduction techniques developed over the last 30 years, have been shown to be effective in reducing the state space explosion problem, particularly in the case of heterogeneous sensor systems, which contain many identical sensor devices. In this thesis we present our approach to verifying Ctrl-MAC, a novel wireless network protocol that supports bidirectional communication of multiple simultaneous physical properties. We explore the extent to which symmetry reduction can aid the model checking process for a sensor network communication protocol. We present our results, and suggest statistical approaches based on our observations of the protocol. We investigate the use of automated tools for the application of symmetry reduction, in particular GRIP, which is well suited for symmetry reduction of wireless sensor network systems. Models of communication protocols often require the use of synchronisation to model the interaction between devices. We present GRIP 3.0, a new version of the tool, which provides support for the use of synchronised transition statements. We provide results from practical work, coupled together with a discussion of drawbacks and future improvements